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知道智慧树答案 
1、单选题：
Consider an object on a rotating disk a distance r from its center, held in place on the disk by static friction. Which of the following statements is NOT true concerning this object?
选项：
A: If the angular speed is constant, the object has a zero acceleration.
B: The object has a tangential acceleration only if the disk has an angular acceleration.
C: The object always has a centripetal acceleration except when the angular speed is zero.
D: If the angular speed is constant, the speed of object is also constant.
答案: 【 If the angular speed is constant, the object has a zero acceleration. 】
2、单选题：
Consider the orbital motion of a planet going around the Sun. Which of the following statements about the motion is true?
选项：
A: Only the mechanical energy of planet is conserved.
B: Only the angular momentum of planet is conserved.
C: Both the angular momentum and mechanical energy of planet are conserved.
D: Neithor of the angular momentum or mechanical energy of planet is conserved.
答案: 【 Both the angular momentum and mechanical energy of planet are conserved.】
3、单选题：
A bullet hits into a hanged uniform rod, the total momentum and total angular momentum of the system are both conserved after collision. Where does the bullet hit?
选项：
A: r = l /3
B: r = l /2
C: r = 2l /3
D: r = 3l /4
答案: 【 r = 2l /3】
4、单选题：
Consider 3 objects with the same mass m but different shapes (solid cylinder, solid sphere and cylindrical shell). They all roll down from rest on an incline without slipping, which one rolls fastest?
选项：
A: The solid cylinder.
B: The solid sphere.
C: The cylindrical shell.
D: They roll equally fast.
答案: 【 The solid sphere.】
5、判断题：
When you watch a clock hanging on a vertical wall, the direction of angular velocity of the second hand is perpendicular to the wall and pointing outside.
选项：
A: 正确
B: 错误
答案: 【 错误】
6、判断题：
If we measure the rotational inertia of an object about different axes, we may obtain different values.
选项：
A: 正确
B: 错误
答案: 【 正确】
7、判断题：
The angular momentum of a particle remains constant if there is no net torque acting on it.
选项：
A: 正确
B: 错误
答案: 【 正确】
8、判断题：
Centrifugal force can be measured in noninertial frames, but it is not a real force, there is no object applying this force.
选项：
A: 正确
B: 错误
答案: 【 正确】
9、填空题：
Calculate the magnitude of net torque on the rod in Figure about the axis through O perpendicular to the page.
答案: 【 [41,42]】
10、填空题：
A box is hanging on a pulley by massless rope, then the system starts to move without slip, How much is the acceleration of m?
答案: 【 [6.5,6.7]】
11、填空题：
How much is the rotational inertia I of a uniform thin disk (mass m, radius R), if the axis is along the line of its diameter?
答案: 【 0.25】
12、填空题：
答案: 【 4】
1、单选题：
An object of mass 0.50 kg, hanging from a spring with a spring constant of 8.0 N/m, is set into a simple harmonic motion. What is the maximum speed of the object if its maximum displacement is 0.10 m?
选项：
A: 0.20m/s
B: 0.40m/s
C: 0.80m/s
D: 1.60m/s
答案: 【 0.40m/s】
2、单选题：
选项：
A: 0.5f
B: 0.707f
C: 1.414f
D: 2f
答案: 【 1.414f】
3、单选题：
Which of the following statements is NOT necessarily true regarding mechanical waves?
选项：
A: They are sinusoidal in nature.
B: They carry energy.
C: They require a medium through which to propagate.
D: The wave speed depends on the properties of the medium in which they travel.
答案: 【 They are sinusoidal in nature.】
4、单选题：
Someone is adjusting a guitar. He changes the length of guitar string from L to 0.9L, and the tension in the guitar string from T to 1.1T. After the adjustment, the frequency of guitar will change from f to ______.
选项：
A: 0.94f
B: 0.99f
C: 1.17f
D: 1.22f
答案: 【 1.17f】
5、单选题：
选项：
A: 
B: 
C: 
D: 
答案: 【 】
6、填空题：
答案: 【 [0.14,0.142]】
7、填空题：
答案: 【 [0.39,0.41]】
8、填空题：
Two traveling waves make a standing wave, and the distance between two nodes is measured to be 10cm. What is the wavelength of traveling wave? λ=___________cm
答案: 【 20】
9、填空题：
答案: 【 1.9】
10、填空题：
答案: 【 [30700,30750]】
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